1. Field of the Invention
The present invention relates to a method of detecting a useful signal affected by noise.
2. Discussion of the Background
One of the great problems in signal processing, simple to enunciate but very complex to resolve, consists in determining the presence or the absence of a useful signal buried in additive noise.
Various solutions can be envisaged. It is possible to use, as a variable, the instantaneous amplitude of the received or processed signal by reference to an experimentally-determined threshold.
It is also possible to use, as a variable, the energy of the total signal over a time slice of duration T, by thresholding this energy, still experimentally.
These thresholdings allow a first assumption on the presence or the absence of the signal. They are, moreover, applicable to any signal. Hence, they are complemented by "confirmation" systems, defining "near-certain" criteria, specific to the type of useful signal, when the nature of the latter is known in advance.
Such a complementary system is widely used in speech processing and may consist, for example, in extraction of "pitch" or in evaluation of the minimum energy of a vowel.